This invention relates to treatment of viral infections using long-chain hydrocarbons in combination with nucleoside analogs, and more particularly to the topical application of therapeutic compositions containing n-docosanol in combination with a nucleoside analog or phosphonoformic acid (PFA).
Viral infections pose a serious threat to the public health. Viruses such as herpes simplex viruses (HSV-1 and HSV-2), cytomegalovirus (CMV), Epstein-Barr virus (EBV), varicella zoster virus (VZV), influenza viruses, human lymphotrophic viruses (e.g., HTLV-1) and human immunodeficiency viruses (e.g., HIV-1) result in significant morbidity and mortality. HSV-1 and HSV-2 are associated with inflammation and lesions of the skin and mucosal membranes, including cold sores, fever blisters and genital herpes lesions. VZV causes shingles and EBV is associated with mononucleosis. Influenza viruses cause flu symptoms and can be fatal. HIV causes acquired immunodeficiency that debilitates and kills infected individuals. Although these viruses may remain latent in some cells and for varying periods of time, generally viral replication results in irreversible destruction of the infected cell producing different clinical manifestations of the diseases they cause.
Most current antiviral therapies employ nucleoside analogs, such as the purine nucleoside analog, acyclovir (ACV), and the pyrimidine nucleoside analog, azidothymidine (AZT), which interfere with viral replication within infected host cells. These nucleoside analogs are converted to their triphosphorylated (nucleotide) derivatives by viral and/or cellular kinases, wherein they block viral DNA elongation. The guanine analog, 9-(2-hydroxy)-ethoxymethyl-guanine, referred to as ACV, possesses potent antiviral activity. Examples of therapeutic nucleoside analogs related to ACV and methods of preparing them are disclosed in U.S. Pat. Nos. 4,199,574, 4,294,831, and 4,360,522 to Schaeffer, U.S. Pat. No. 5,580,571 to Hostetler, U.S. Pat. No. 5,756,737 to Turchetta et al., and U.S. Pat. No. 5,567,816 to Schloemer et al.; the disclosures of which are incorporated herein by reference. The main problems involved in the use of these nucleoside analogs are their limited phosphorylation in some cells and the cytotoxic side effects of the nucleoside analog triphosphates. Moreover, these antiviral drugs can potentially act as mutagens and/or teratogens in host cells. Thus, despite the potent antiviral activities of the nucleoside analogs, less toxic, efficacious therapies have been sought.
Among the alternatives to the nucleoside analogs for treatment of viral infections, are a variety of long-chain alcohols, fatty acids, alkanes and related compounds. Early work with such compounds focused on their direct viricidal effects. For example, unsaturated alcohols having from 14 to 20 carbons and one to four double bonds have been reported to possess antiviral activity. The most effective of these unsaturated alcohols was γ-linolenyl alcohol, a C18 alcohol with double bonds at positions 6, 9 and 12 (Sands et al., Antimicrob. Agents & Chemother. 15:67–73, 1979). Compositions containing oleic acid (C1 8, one double bond) have also been shown to exhibit anti-herpes virus activity (PCT patent application WO 9602244A1).
Long-chain aliphatic alcohols having from 20 to 32 carbons have been shown to possess antiviral and anti-inflammatory activities. Therapeutic compositions containing such long-chain aliphatic alcohols and related compounds are described in U.S. Pat. No. 4,874,794, U.S. Pat. No. 5,071,879, U.S. Pat. No. 5,166,219, U.S. Pat. No. 5,194,451 and U.S. Pat. No. 5,534,554; the disclosures of which are incorporated herein by reference.
Some compounds that are structurally related to long-chain aliphatic alcohols have also been reported to possess antiviral activity. For example, U.S. Pat. No. 4,513,008 discloses the antiviral activity of C20 to C24 linear polyunsaturated acids, aldehydes or alcohols having five to seven double bonds. Compounds having a long chain fatty acyl group, containing at least three unsaturated bonds, attached to a nucleoside or nucleoside analog are also disclosed as antiviral treatments in U.S. Pat. No. 5,216,142. Related U.S. Pat. No. 5,276,020 discloses antiviral compounds having a C16, C18 or C20 long chain fatty acid group attached to a nucleoside analog and a method of treating virus infection using these compounds. Indeed, Hostetler et al. recently reported enhanced oral absorption and antiviral activity of a C18 derivative of ACV, 1-D-octadecyl-sn-glycero-3-phospho-ACV (Hostetler et al., Biochem. Pharmacol 53:1815–1822, 1997).
Topical therapies comprising various alcohols, fatty acids and amines have also been reported. For example, antiviral activity was reported for liposomal AL721, a mixture of neutral glycerides, phophatidylcholine and phosphatidylethanolamine (Antonian et al., Neurosci. Biobehav. Rev. 11:399413, 1987). Antimicrobial compositions for topical treatment containing a C15 glycerol monoester of lauric acid or a polyhydric alcohol monoester of lauric acid with a mixture of fatty acids (C10 capric and C8 caprylic acids) were disclosed in U.S. Pat. No. 5,208,257. Treatment of herpes lesions using topically administered compositions containing an anesthetic, a surfactant and a topical carrier were disclosed in U.S. Pat. No. 5,380,754. A method of treating inflammation by topically applying ethyl-cis,cis(9,12)octadecadienoate (ethyl linoleate) was disclosed in U.S. Pat. No. 4,025,645 as a cold sore treatment.
Katz et al. (Proc. Natl. Acad. Sci. USA 88:10825–10829, 1991; U.S. Pat. No. 5,534,554) have shown that one particular long-chain aliphatic alcohol, n-docosanol (C22), possess potent systemic and topical antiviral activity against a range of viruses, including herpes simplex virus (in vitro and in vivo), HIV-1 (in vitro), respiratory syncytial virus (in vitro) and Friend virus (in vitro and in vivo). Unlike C10 to C18 unsaturated alcohols which exhibit detergent-like antiviral activity, n-docosanol does not inactivate viruses directly (Katz et al., Proc. Natl. Acad. Sci. USA 88:10825–10829, 1991; Snipes et al., Antimicrob. Agents Chemother. 11:98–104, 1977). Progressive binding and uptake of n-docosanol by cells may account for its antiviral activity because pre-incubation of cells with the alcohol produces optimal antiviral activity. Moreover, 70% of cell-associated n-docosanol is found in cell membrane components and the remainder is associated with soluble cell fractions (Pope et al., J. Lipid Res. 37:2167–2178, 1996). Plasma membrane incorporation of n-docosanol does not inhibit virus binding to the cell surface. Early viral protein synthesis was inhibited by more than 80% and viruses did not localize to nuclei (Katz et al., Proc. Natl. Acad. Sci. USA 88:10825–10829, 1991). Fusion of the virus with the plasma membrane of the cell is inhibited (Pope et al., Antiviral Res. 40:85–94, 1998).
The inhibition of viral protein synthesis and antiviral activity of n-docosanol appears to require cellular metabolism of the alcohol (Pope et al., J. Lipid Res. 37:2167–2178, 1996; Katz et al., Ann. N.Y Acad. Sci. 724:472–488, 1994). Moreover, while intracellular metabolic conversions of n-docosanol may account for its antiviral activity, (Katz et al., Annals N.Y. Acad. Sciences, 724:472–488, 1994), n-docosanol is not cytotoxic at concentrations up to 300 mM.
Compounds, such as n-docosanol, whose pharmacologic effects are mediated by cellular metabolism may alter the way a second drug may be metabolized and expressed. In addition, viruses are known to dramatically alter host cell metabolism. Such drug interactions can produce undesirable effects in patients being treated with multiple drugs. However, beneficial drug interactions can also occur. Indeed, there have been numerous reports about interactions between nucleoside analogs, such as ACV, and compounds which modulate cellular metabolism (Spector et al., Proc. Natl. Acad. Sci. USA 86:1051–1055,1989; O'Brien et al., Antimicrob. Agents Chemother. 34:1178–1182, 1990; Hirsch et al., 1996 Antiviral agents. In Fields Virology Third Edition, B. N. Fields, D. M. Knipe, P. M. Howley, eds. Lippincott-Raven Publishers, Philadelphia, pp. 431–466). Generally, the mechanism involves modulation of one or more steps in cellular nucleoside uptake or metabolism resulting in a more efficient expression of antiviral activity.
Because patients with recurrent herpesvirus disease could be concurrently treated with n-docosanol 10% cream and acyclovir (ZOVIRAX™), the potential for either detrimental or beneficial drug interactions was investigated. The present invention is based on the findings that n-docosanol synergistically intensified the antiviral activity of nucleoside analogs against replication of several herpesviruses and vaccinia virus.